Microbiological Diagnosis of Chest Infection

Question 1

What is 4 examples of diagnostic techniques

Answer 1

Microscopy and culture of sputum and blood
Antigen detection methods
Nucleic acid amplification (PCR)
Serology (antibody measurement)

Question 2

What do you gram stain sputum for

Answer 2

organelles and pus cells

Question 3

What is of better value than gram staining in microscopic diagnostic of chest infection

Answer 3

culturing for major respiratory pathogens overnight

Question 4

What are the major respiratory pathogens

Answer 4

Strep pneumoniae
Haemophilus influenzae
Moraxella catarrhalis

Question 5

What does previous antibiotic therapy select out

Answer 5

organisms like e.coli and staph aureas that are not respiratory infections but part of the normal flora

Question 6

Is TB detected by gram stain?

Answer 6

No, ZN or Auramine phenol stain
or Acid and Alcohol Fast Bacilli (AAFB) - resist decolorisation by acid or alcohol
needs special culture conditions

Question 7

When is identification of TB finally possible

Answer 7

once it has fully grown

Question 8

What gives an accurate diagnosis of lower respiratory tract infection by minimising contamination

Answer 8

bronchial alveolar lavage

Question 9

Explain a bronchial alveolar lavage procedure

Answer 9

a bronchoscope is passed through the mouth or nose into the lungs and fluid is squirted into a small part of the lung and then collected for examination

Question 10

What is bronchial alveolar lavage useful in helping to diagnose

Answer 10

ventilator associated pneumonia

Question 11

When should blood cultures be taken

Answer 11

Any patient with severe sepsis
Patients with bacteraemia due to pneumonia
SEVERE DISEASES

Question 12

what is the steps in blood culture

Answer 12

Blood inoculated into two bottles containing culture media and incubated
taken to microbiology unit
machine beeps when you have a positive result
post 48 hours nothing found, results = negative

Question 13

Following positive result of blood culture what steps occur next

Answer 13

day 1: Overnight subculture of sensitivity and identification tests
day 2: full ID, check sensitivity and clinical significance

Question 14

Why is the clinician contacted by the microbiology unit

Answer 14

to inform the result ensuring proper treatment is given by recommending most efficient antibiotic

Question 15

What are some example of organisms that aren’t easily cultures

Answer 15

Legionella pneumophila
Mycoplasma pneumoniae
Chlamydia psittaci (birds)
Coxiella burnetti (Q fever)
(legit ella my cock burns, chlamydia)

Question 16

What is a non culturing method for demonstrating the presence of another organism

Answer 16

Specific antigen detection

Question 17

Where can Legionella and pneumococcal antigens be detected

Answer 17

Urine

viruses in naso-pharyngeal secretions (snot)

Question 18

Define agglutination

Answer 18

reaction in which particles suspended in a liquid collect into clumps and which occurs especially as a serological response to a specific antibody

Question 19

What is different ways antigen detection can occur

Answer 19

agglutination
EIAS
Immunofluorescence

Question 20

How does Immunofluorescence work in antigen detection

Answer 20

location of an antigen in tissues by reaction with an antibody labelled with a fluorescent dye.

Question 21

What occurs in latex agglutination

Answer 21

latex particles coated in monolocal antibodies and are mixed with clinical specimen in answer, if organism present an agglutination will form

Question 22

What does EIA stand for

Answer 22

Enzyme Immuno-Assay

Question 23

What does ELISA stand for

Answer 23

Enzyme Linked Immunosorbent Assay

Question 24

What are EIA and ELISA both

Answer 24

specific antibody detection test, detects antigen and produced a colour change by enzyme linked on second antibody

Question 25

The more antigen present in an ELISA results in what

Answer 25

the more colour change

Question 26

What is the steps in the DNA detection of PCR

Answer 26

DNA opens up by denaturing Primers attach to complimentary base - anneal multiple copies then produced as it extends

Question 27

The primers have what kind of sequence in PCR

Answer 27

short oligonucleotide

Question 28

When do you know detection is positive in PCR

Answer 28

If primer bind to target = amplified copies of DNA easily detected

Question 29

What is the disadvantaged of PCR

Answer 29

very sensitive | many false positives due to contamination

Question 30

How do respiratory diagnoses occur through PCR

Answer 30

respiratory samples collected e.g. through throat/flocked swabs then screened for wide range of respiratory viruses

Question 31

What is the different respiratory viruses you could be screened against in PCR

Answer 31

``` Influenza A and B Adenovirus RSV Parainfluenza viruses Metapneumovirus Coronavirus Rhinovirus (in paramount met a rhino, RSVP add corona) ```

Question 32

What do serology tests measure

Answer 32

The antibodies in your bloods

Question 33

What does it mean if IgM is present in a Serological Diagnosis

Answer 33

IgM is a marker of current infection

Question 34

What does it mean if IgG is present in a Serological Diagnosis

Answer 34

IgG marks previous infection

Question 35

Why would the total number of antibodies be measured in a Serological Diagnosis

Answer 35

to show the rising titre

Question 36

Does it take a short or a long time for antibody numbers to rise

Answer 36

long time

Question 37

What is antibody measurement mostly used for these days

Answer 37

to determine immunity - vaccination response

Question 38

What is the rising titre

Answer 38

increase in the levels of antibodies over the course of an illness